DE29914825U1 - Apparatus for performing a cable end surface finishing process - Google Patents

Description

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Device for carrying out a cable surface finishing

lation procedure

The invention relates to a device for severing a cable according to the preamble of claim 1 and for carrying out the method according to the preamble of claim 5.

Cables in the sense of the invention are basically understood to mean electrical or light-optical insulated or non-insulated conductors, in particular POF optical fibers, with or without one or more sheath layers.

WO-A-98/13907 provides information on a structure for cutting and stripping a cable. The "cut and strip" machine shown there has knife holders into which different knives can be inserted next to each other, so that different operations can be carried out on a cable one after the other. With such a known machine, cables can be cut and stripped with good success. With certain cables, in particular with POF optical fibers, there are certain problems due to the material, the solution of which is the object of the invention.

POF optical fibers and other cables made of certain materials tend to suffer deformations, disruptions in the material structure, cracks, brittle fractures, micro-fractures, etc. when cut. These deformations and disruptions reduce the application quality of the cut cables. The present invention eliminates this disadvantage and improves the cutting quality - in particular the quality of the cutting surface itself.

Of course, it was already known to re-cut copper cables if normal cutting caused severe deformations on the

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cable end. Another piece of copper conductor was simply cut off, e.g. after the sheath layers had been removed. However, an improvement in the quality of the cut surface itself was hardly achieved and was not even sought; only plastic deformations in the copper (oval-shaped conductor ends) were cut off by cutting the conductor again.

Various processes have been used to try to improve the quality of cable end surfaces. The cut surfaces have been re-milled with a milling cutter, polished, or, for example in the case of POF cables, they have been treated with heat (hot plating). All of these known processes are very complex and require a relatively long treatment time and usually additional different tools. In addition, the known processes cause additional contamination problems.

The invention is based on the object of developing a new device for carrying out a new method and a new device with which a good cutting surface refinement can be achieved and the additional effort is kept relatively low.

The solution lies in four steps, which can be used independently of one another and each improves the cutting quality; the steps or measures that contribute most to solving the problem are defined in claims 1, 5 and 6. Improved solutions with further integration and further advantages over the prior art are set out in the dependent claims. The new device sets the following steps:

a) After cutting a cable, the cable is cut at least once, preferably more often, immediately next to the cutting point, whereby the distance between adjacent

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Cuts are between 10 and 0.001 times the cable diameter, preferably between 1 and 0.005 times the cable diameter, in particular between 0.3 and 0.005 times the cable diameter or the diameter of the central conductor of the cable. For a POF optical fiber that is 1mm thick, for example, the distance is preferably between 1mm and 0.01mm, preferably between 0.3mm and 0.05mm, in particular between 0.2mm and 0.1mm. Before the particularly thin slices are cut off, a coarser cut with 1mm cut off slices can also preferably be made. Preferably, re-cutting is carried out about 1 to 10 times, in particular about 3 to 8 times, e.g. 5 times. For all cables, this leads to an improvement in the quality of the cable end faces. In the case of POF cables, this particularly means that the cracks and material breakouts and brittle residual fractures that occur during normal cutting are eliminated or at least completely displaced to the cable periphery.

By removing cable material in a disc-like manner, defects on the cable end surface that occurred during the first cut are reduced or removed. However, since the subsequent cuts only remove very thin layers from the cable, essentially no new defects arise and the aim of the invention is achieved to some extent.

b) Additionally or alternatively, a particularly thin knife is used as the knife. This is known to the expert as obvious, that thinner knives result in fewer deformations at the cutting point or fewer disruptions, but thin knives are known to be subject to very high levels of wear; therefore, according to the invention, a new type of knife is preferably used which is particularly thin only in the immediate cutting area (e.g. razor-thin), but of normal thickness besides. To further reduce wear, according to a further improvement, at least two different knives can be used.

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A conventional, wear-resistant knife (e.g. a V-knife) for the first cut and a second knife with a particularly thin blade for the subsequent cut. According to one variant, several thinner knives, e.g. with decreasing cutting thickness, can be used to increase the service life of the arrangement overall while maintaining optimal cutting quality.

c) Additionally or alternatively, the cable is centered directly at the cutting point and held in a centered position by a special holder so that it cannot move, so that the knife hits a cable that is held in a particularly fixed position and centered. Centering cables to improve the cutting quality is standard - especially for coaxial cables - but with conventional "cut and strip" machines, no particular importance is attached to centering in the immediate cutting area because - according to conventional expert opinion - when a cable is cut through, it is cut through completely anyway and there is no risk of damage to central conductors or the like, which is why special centering could be dispensed with. It was only when the inventors discovered that cables that are not held centered have a poorer cutting quality that this new measure according to the invention was developed.

d) Additionally or alternatively, two counter-rotating knives are used which cooperate with one another, one of which has a thin cutting edge as per b) and the other of which has a relatively wide counter-cutting edge at about 90 degrees, which serves more as a support for the cable than as a cutting edge, although the two cutting edges are moved past one another in the form of a shearing movement. In this case, either both knives can be moved in a radial direction relative to the cable axis, or one of the knives is radially rigid with respect to the cable axis and the other knife can be moved radially.

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If the cables are not only to be severed but also stripped, the cuts in the cable sheath, particularly in POF fiber optic cables, are preferably made by additional, upstream rotating blades, as is basically shown in the aforementioned WO-A. Using conventional "die blades" or conventional V or radius V blades, after carrying out the desired one of the four individual steps - ideally after carrying out all steps a-d - the cable, which has already been cut in a rotary manner or not cut at all, is freed from its sheath.

In the case of POF fiber optic cables with multiple sheath layers, the outermost sheath layers can alternatively be removed before steps a-d are applied. According to the invention, the effect is used that any remaining residual disturbances on the cut surface of the cable caused by knives or cutting are shifted to the area of the sheath and the inner conductor has an optimal cut surface - and thus low attenuation during light transmission.

In the case of cables without a sheath, the cut surfaces are more even; any residual defects also only occur at the edge areas, since they are cut away in the middle areas by the method according to the invention, without causing any new significant defects at the same time. This effect according to the invention is obviously related primarily to the elimination of significant supporting forces from the cable end piece to be severed. The thinner the discs to be severed according to the invention, the lower the supporting forces and the lower the cutting forces required and the lower any deformations, cracks, etc.

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Further improvements and details according to the invention emerge from the drawing, which shows a symbolic embodiment according to the invention.

They show:

Fig. 1 is a symbolic view of a cutting process using conventional devices. Cutting stages 1-4 show the cutting process and it can be seen that the special material structure (e.g. POF) results in an unclean cut surface. According to the state of the art, this would have been post-treated by grinding, milling, polishing or melting, for example.

Fig. 2 new knife types a)-c), which according to the invention work together with a new cooperating knife type d). Type a) has a slanted cutting edge and is milled in the middle area like a notch down to a very thin cutting edge.

Type b) has a straight cutting edge with a similar milling and a pre-centering V-shaped inlet. Type c) is designed like a radius V-blade with a round cutting edge and has a similar milling. The millings are approximately the same width as the expected cable thickness and a length that is slightly longer than the expected cutting movement through the cable. Type d) is also designed like a radius V-blade, but is significantly thicker than a knife, so that its round cutting edge forms a right angle in the cut. The material thickness of this cutting edge thus serves as a centering base for the cable. Type d) also has a V-shaped centering inlet that is milled at its base so that an inserted cable can be centered and positioned there.

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is held in position when a counter knife e.g. type a), b) or c) cuts off a slice.

Fig. 3 two new hold-down devices that cooperate with the knife type d) according to Fig.2 and press a cable - before the cut - into the centering recess on the knife d). Both hold-down devices preferably also have a radius recess with which they grip the cable and reinforce the centering effect of the knife type d). The hold-down device a) can be used for an adjacent knife type d), while the hold-down device b) is equipped with an extension for cooperation with a more distant knife of type d), as can be better seen in Fig.4-6. The hold-down device can be driven pneumatically, for example, and has a hold-down arm - if necessary with a semicircular centering recess for the cable sheath, which can be pressed onto a cable;

Fig. 4 shows two knife arrangements on a "cut and strip machine" according to Fig. 7, where picture a) shows a rotary cutting head according to the aforementioned WO-A with connected conveyor belts and clamped cable, while pictures b) and c) show the linear cutting head with laterally movable knife holders according to the aforementioned WO-A. In b), the first (rough) cut is prepared with a wear-resistant conventional knife; in c), the cable already pre-cut according to b) is repetitively re-cut by the new knife arrangement according to the invention, as also according to Fig. 5 picture a);

Fig. 5 another illustration of the cutting unit according to Fig.4 b) and c) and a removal unit with

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Conveyor belts after the knife block for the cut and, if necessary, stripped cable. Figure b) shows the stripping process in which a cable sheath previously cut by the rotary knife arrangement as shown in Fig.4 a) is pulled off by the wear-resistant pair of knives.

Fig. 6 is another illustration of the linear cutter head according to Fig.4 and 5, whereby the rear end of the cable piece produced according to Fig.4 b)-c) and Fig.5 a)-b) is now severed (a), or corrected (b) and stripped (c), so that the end product is a cable piece cleanly severed and stripped on both sides. At the middle cutter position, the cutters are arranged in a mirror image of the arrangement at the right-hand position;

Fig. 7 a “Cut and Strip* machine according to the mentioned WO-A with built-in knives and hold-down devices according to the invention;

Fig. 8 shows the sequence of a stripping process in a device according to the invention with four re-cuts on a POF optical fiber cable with one sheath layer;

Fig. 9 shows the comparable process of a stripping process according to Fig. 8 on a POF optical fiber cable with two sheath layers using a device according to the invention. With such cables, the second, inner sheath layer usually remains on the optical fiber, so that further stripping of this second layer is not necessary. For better cable finishing, as shown, it is recommended to strip the first sheath layer beforehand;

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Fig. 10 is a photograph of POF optical fibers without cladding cut by conventional V-knives;

Fig. 11 is a photograph of a POF optical fiber without a sheath cut by hand using a razor blade;

Fig. 12 is a photograph of a POF optical fiber cable severed by means of a special knife according to the invention with a thin blade and centering approximately 1 mm after the cut with a conventional knife;

Fig. 13 is a photograph of a cable end which has been recut twice by means of a special knife according to the invention with a thin blade and centering, after 1 mm and then after 0.2 mm after the respective last cut;

Fig. 14 to 20 and 22 further photographs of cables which have been recut several times, with the number of cuts and the width of the recut cable piece in mm indicated on the left; in Fig. 14 the information means e.g.: 1 severing cut with a cable end piece disc of 1mm and two cable end piece discs each with a width of 0.2mm.

Fig. 21 is a photograph of a cable end without a sheath produced by means of a special knife according to the invention with a thin blade but without holding down (impaired centering);

Fig. 23 two photographs of a POF optical fiber cable end severed according to the invention with originally two sheath layers and with one remaining sheath layer; In Figs. 10-22, the respective attenuation achieved by the experimentally achieved interfaces is shown next to the photographs.

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POF optical fiber specified.

Fig. 24 a photograph of the casing cut by rotary knives a) and a photograph of the casing severed by conventional die-blades;

Fig. 25 an exemplary list of the time sequence of a complete stripping and cutting process according to the invention on a POF optical fiber cable and

Fig. 26 shows an example arrangement of new types of strip modules. These are cable processing devices that carry out individual processing steps in the course of complete cable processing for optical fibers. On the left in the picture there is a module with clamping jaws according to the invention and a pair of knives that carry out the end face processing according to the invention on a cable end. Next to this there is a module with which, for example, Kevlar® fibers or the like can be cut (punched) out of a cable sheath. Next to this there is a module with a rotary cutting head, which can be used, for example, for rotary cutting into a cable, and on the right in the picture there is a module for removing coating from an optical fiber. The individual working methods of the three modules on the right and their specific structure have been made known by the Schleuniger machine FO 7045, in which these functions are integrated. The new and advantageous feature of the modular structure shown here is the better utilization of the individual modules or work processes, since, in contrast to the FO 7045, several work processes can be carried out on several cables at the same time and one work process on one machine does not block other work processes.

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The module on the left in the picture is completely new and inventive, as it is equipped in such a way that it enables the inventive separation of thin slices from the end of a cable for the first time. With conventional stripping devices or cable cutting devices, it was never thought of and therefore not intended to be possible to separate slices in the tenth of a millimeter range from a cable.

However, the measures required to convert existing stripping devices or cable cutting devices are understandable to a person skilled in the art once he is familiar with the teaching of this application. Maximum guidance precision, small axial displacements in the hundredth to tenth of a millimeter range and corresponding blade qualities according to the invention as well as preferably a suitable hold-down device in the cutting area allow the cable end face treatment according to the invention.

Further details and variants of the invention are specified in the claims.

The device was demonstrated by the inventors to an interested foreign audience during tests at an in-house scientific conference in Thun, Switzerland, in March.

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Claims (13)

1. Device for a cable end surface finishing process on a severed cable end piece with at least one knife in a cable processing device, characterized in that the knife or the cable processing device can be controlled so that the cable end is severed (recut) again with the knife at least once, preferably several times, at a short distance from the respective cable end, so that only a thin slice of the cable is severed from the remaining cable end, the thickness of the slice being selected so that lower cutting forces occur during the separation than when the cable is severed for the first time. 2. Device according to claim 1, characterized in that for the first re-cutting or for all subsequent cutting operations, thin knives with preferably very thin cutting edges are provided, which are optionally arranged next to knives for the first (normal, conventional) cut, wherein a relative displacement can be carried out between the knives and the cable in order to achieve the respectively required knife/cable position during cutting operation. 3. Device for finishing the cable end surface at a cable end by means of a knife, in particular according to claim 1 or 2, characterized in that the cable is held centered and positioned in the immediate vicinity of the knife during the cutting - preferably by a special design of the knife or at least one knife involved - and that the cut is made with the knife close to the cable end. 4. Device for finishing the cable end surface at a cable end by means of a knife, in particular according to claim 1, 2 or 3, characterized in that the cable end can be held firmly and in position in the immediate vicinity of the knife by means of a clamping device during the cutting, preferably against a base or against another knife cooperating with the knife. 5. Device for finishing cable end surfaces with at least one knife device, a knife device holder and a drive for the knife device holder, and with a cable or knife feed along the cable axis, characterized in that the drive and the cable or knife feed are assigned a control which, after a severing cut, carries out at least one severing cut of a thin slice from the cable end - preferably automatically. 6. Device for finishing cable end surfaces with at least one knife device, characterized in that the device comprises a device which allows the separation of slices from the cable end which are so thin that the thickness of the slices only makes up a fraction (e.g. 1-30%, in particular e.g. 5-20%) of the cable thickness. 7. Device according to claim 6, characterized in that the device comprises a hold-down device and/or a centering device in the immediate vicinity of the knife. 8. Device according to one of claims 5 to 7, characterized in that the knife or the knife device is particularly thin in the region of its cutting edge - preferably thinner than 0.3 mm. 9. Device for cutting a cable with a knife, in particular according to one of claims 5 to 8, characterized in that the knife or the knife device has a milling in the region of its cutting edge with approximately the width of the cable to be cut, which milling leaves a thin cutting edge of preferably thinner than 0.3 mm and corresponds at least to the cable width. 10. Device according to one of the preceding claims 5 to 9, characterized in that the or a knife of the knife device has a centering - e.g. V-shaped - milling, at the base of which the milling corresponds to the cable diameter, so that an inserted cable can be held in position there. 11. Device for cutting a cable with two cooperating blades, in particular according to claim 6 or 7, characterized in that one of the two blades has an at least approximately rectangular cutting edge and a relatively large thickness, which serves as a base for a cable to be cut and as a counter-bearing for the cutting blade shearing past it. 12. Device for severing a cable with two cooperating blades, in particular according to one of the preceding claims 5 to 11, characterized in that a cable locking or holding-down device is assigned which, in cutting operation, holds the cable in the immediate vicinity of the blade during the cutting process, preferably holding it pressed against a blade according to claim 10 or 11. 13. Device according to one of the preceding claims 5 to 12, characterized in that the knife device has at least two knives or knife devices or at least two sheaths or cutting devices, of which one is particularly wear-resistant and is intended for the first cut, while the other has a particularly thin blade for subsequent cutting, and that the knives are mounted on a common knife holder.